Abstract: In high technology industries ceramics have several uses, especially at high temperature, e.g. inert crucibles, electrodes and catalysts. We are working on production and development of new oxide ceramics, based on complex cubic perovskite structure, for fabrication of crucibles for metallurgical applications. In the present work, we have produced and studied sintering behavior of a new ordered complex cubic perovskite oxide ceramic Ba2HoWO5.5. Microstructural characteristics of the Ba2HoWO5.5, sintered between 1200 to 1400°C for 48h, were studied by scanning electron microscopy. The mechanical behavior was studied by Vickers microhardness tests. Our studies show a gradual improvement in microstructural characteristics of sintered Ba2HoWO5.5, both on polished and fractured surface. This homogeneity of grain sizes and particle size distribution increases with the increasing of the sintering temperature, which results in higher sintered density and increased mechanical hardness.

Abstract: A model for designing sandwich nanocomposite ceramic tool materials with symmetrical distribution was presented. By adding nano-sized Al2O3 particles into the submicro-sized Al2O3 and TiCN, Al2O3/TiCN sandwich nanocomposite ceramic tool materials were fabricated by means of powder-laminating and hot-pressing technique. The experimental results showed that optimal mechanical properties were achieved for the composite with the addition of 35 vol.% TiCN particles in the middle layer and 45 vol.% TiCN particles in the outer layers, layer thickness ratio is 0.3, with the flexural strength reaching respectively 900MPa，fracture toughness and Vicker's hardness in the surface layers being 6.5MPa•m1/2 and 19.2GPa.

Abstract: The erosion wear resistance of YSZ ceramics is worth studying because solid particle erosion is one of the main causes of destroying the materials and apparatuses. In this paper, 8YSZ ceramics reinforced by NiCr alloy and Al2O3 particles were pressureless sintered at an optimized sintering condition. The facture toughness reached a maximum value of 4.6 MPa•m 1/2 when the addition of NiCr alloy is 12 vol.%, which was much higher than that of the pure 8YSZ ceramic (2.0 MPa•m 1/2) fabricated in the same condition. Solid particle erosion wear behavior of NiCr-Al2O3-ZrO2 (8Y) ceramics composites was performed by self-designed sand blasting type solid particle erosion wear equipment, using 36# SiC particles as abrasive particles with the 90o erosion angle. The effect of the volume addition of NiCr alloy on the erosion wear of NiCr-Al2O3-ZrO2 (8Y) ceramic composites at room temperature was investigated. The results show that the volume erosion rate of the ceramic composites decreased as the volume addition of the NiCr alloy increasing. Crossing cracks, plastic deformation and minor chipping are the major erosion mechanisms.

Abstract: 2024Al and SiC/2024Al were used to encapsulate the AD95 Al2O3 ceramics by Vacuum-high Pressure Infiltration Method. Their anti-bullet properties are not good with Efm of 5.17 and 4.65 respectively, and is far lower than that of the ceramic without encapsulation. The latter one can generate higher hydrostatic pressure between the bullet and ceramic during penetration process. However, in encapsulated targets, the ductile materials in front of the ceramic can decelerate the bullet, so the pressure between bullet and ceramic is not great enough to break the bullet. Propagated microcracks along with the bonding interface were observed in plates consisting of encapsulated Al2O3. These microcraks lead to the interfacial debonding between Al2O3 and encapsulating materials. Consequently, the anti-bullet property of the ceramic encapsulated by metal or composite is depressed. Further more, the different interface bonding conditions and fracture modes cause the discrepancy of anti-bullet property in two kinds of targets with encapsulation structure.